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Invalid Client Error When Requesting Access Token in Cerner Paid Sandbox

Rohit SinghNov 12 2025

I’ve purchased a Cerner sandbox plan and successfully created an application in the Cerner Code Console.

Using the base URL and tenant ID provided after the purchase, I’m able to retrieve the .well-known configuration successfully.

However, when I try to obtain an access token using the following endpoint:

https://authorization.sandboxcerner.com/tenants/1ca6b88d-7a01-4231-91dd-6fbfc1bb7bbe/hosts/fhir-ehr.sandboxcerner.com/protocols/oauth2/profiles/smart-v1/token
I’m getting this response:

{
  "error": "invalid_client"
}

I’ve verified that my client_id and client_secret are correct and match the credentials shown in the Code Console.

I have a couple of questions:

  1. Do we need to link or connect the client application created earlier (in the Code Console) with the paid sandbox environment manually?
  2. Our integration type is backend-to-backend (system-to-system) — is there any additional configuration required for this type of setup in the sandbox or Code Console?

Any clarification or a sample working token request for a backend-to-backend setup would be greatly appreciated.

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Added on Nov 12 2025
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